switch to gradle

gradle files added
gradle: plugins added
build: files added
.travis.yml: gradle cache stored
distribution: tar and zip file stuff added
broker/build.gradle: osgi plugin added
build: bintray upload added
pom: files removed
distribution: assembly.xml removed
gradle: test ouput added to sub builds
.editorconfig: gradle files added
build: wrapper task added
osgi: added to h2_ and mapdb_storage
gradle: files cleaned
build.gradle: jars used for tar/zip

settings.gradle

@@ -0,0 +1,16 @@
+rootProject.name = 'moquette-parent'
+include ':moquette-broker'
+include ':distribution'
+include ':moquette-h2-storage'
+include ':moquette-mapdb-storage'
+include ':moquette-embedded-test'
+include ':moquette-osgi-test'
+include ':moquette-performance'
+
+project(':moquette-broker').projectDir = "$rootDir/broker" as File
+project(':distribution').projectDir = "$rootDir/distribution" as File
+project(':moquette-embedded-test').projectDir = "$rootDir/embedding_moquette" as File
+project(':moquette-osgi-test').projectDir = "$rootDir/osgi_test" as File
+project(':moquette-performance').projectDir = "$rootDir/perf" as File
+project(':moquette-h2-storage').projectDir = "$rootDir/h2_storage" as File
+project(':moquette-mapdb-storage').projectDir = "$rootDir/mapdb_storage" as File